Metering pump



Dec. 31,1957

H. R. LUNDSTROM METERING PUMP Filed June. 17. 1954 United States Patent METERING PUMP Harold R. W. Lundstrom, Waltham, Mass, assignor to W. H. Nichols Company, Waltham, Mass., a corporation of Massachusetts Application June 17, 1954, Serial No. 437,528

2 Claims. (Cl. 103-426) It is now practice to, employ in the spinning of most synthetic textile fibers small precision metering pumps to govern the flow to the orifices which form the individual fibers by extrusion of the synthetic material. These pumps operate under high pressure on the order of 5,000 pounds per square inch and at. slow speeds, such as 20 R. P. M.

The bearing loads on the teeth and journals of such pumps are high so that hard durable materials must be used in the pump construction. Likewise the process is carried out at relatively high temperatures such as 600 F. Further, the molten nylon or other polymer carries suspended therein abrasive powders which tend to wear away the pump. Hence the materials, such as steel, used to make these portions of spinning pumps directly contacting the molten material are necessarily hard, resistant to abrasion and resistant to softening at elevated temperatures. Such materials are very difficult to machine in either the annealed or the hardened and tempered state, containing as they do large percentages of alloying elements needed to meet the conditions imposed.

A disadvantage of the pumps as heretofore made lies in the presence of a discharge groove in the adjacent face of one of the hard plates leading from a pair of metering gears across one side face of one of the gears to the hollow of a hollow stud on which that gear is journaled. The liquid in this groove being at high pressure, imparts a thrust on the gear equal to the discharge pressure multiplied by the groove area exposed to the gear, and as this pressure is exerted eccentrically it causes tipping of the gear which results in spot wear on the confronting plates and on the gear-supporting stud, particularly because of the presence of the abrasive elements contained within the molten material handled by the pump.

An object of the invention, therefore, is to relieve the gear from this thrust, and this is accomplished by forming the discharge groove or passage leading to the hollow stud on which the gear is journaled in a part which is spaced from the gear face. This passage may be in a housing frame part which is of relatively easily ma chinable material, and in this case, the formation of a hole through one of the hard plates is all that is necessary in that plate to provide for the discharge of molten material from the pump. If desired, however, the passage leading to the hollow of the hollow stud may be formed in that face of the hard plate which is remote from the gears, since the cutting of an open groove in the hard plate is not too diflicult.

For a complete understanding of this invention, reference may be had to the accompanying drawings in which Figure l is a side elevation of a double discharge metering pump embodying the invention.

Figure 2 is an end elevation of the same.

Figures 3, 4'and 5 are detail sectional views on the correspondingly numbered section lines of Figure 2.

Figure 6 is a view similar to Figure 1, but showing a single pump of the same capacity as the double pump of Figure 1.

Figure 7 is a detail sectional view similar to a portion of Figure 5, but showing a modification.

Referring first to Figures 1 t0 3, which show a double pump, this pump comprises two pairs of intermeshing gears 1, 2 and 3, 4, respectively. These gears are mounted within cut-outs of a pair of hard plates 5 and 6 which form peripheral casing members for the gears, and on opposite sides of the gears there are positioned plates 7, 8 and 9 which'overlie the faces of the gears and provide end walls for the pump chambers making close clearances with the gears. The plate 8 is common to the two sets of gears, being positioned between them. 1

All these plates 5,6, 7, 8 and 9 are formed of very hard materials capable of withstanding high temperatures and normally these are formed of alloy steels, the alloys being such as to impart the desired hardness and heatresistant characteristics desired. Such alloys are old and well known and per se form no part of the present invention.

These plates are held together and to one or more casing or end plates 20 by suitable means such as bolts 15, preferably engaging threads in holes 16 in the end plates 20 which may be of material less difficult to machine since they do not come into contact with the hot molten materials and are therefore not required to be made of such hard durable materials as the plates 5, 6, 7, 8 and 9.

One of the gears of each pair 'is arranged to be power driven and is thus suitably secured as by keys, as shown in :Figure .4, to adrive shaft25. This drive shaft is mounted for rotation in bushings 26 in mating holes in the plates 7, 8 and 9. The shaft extends into a recess 27 in the end plate 20. The extension is in the form of a non-circular section which engages loosely a similar noncircular socket in a driving element 28. This driving element is retained in position within its housing formed by the recess 27 as by means of a flange member 29 which may be secured to the end plate 20 as by means of cap screws 30. The outer face of the driving element 28 is formed with a non-circular socket member 31 in which may be projected a similar shaped end portion of a drive shaft (not shown) of a suitable power rotating device.

The shaft 25 is shown as provided with a central bore 35 therethrough which opens out at opposite ends, one end into the socket 48 of the drive element 28 and at the other end outwardly of the plate 7. The provision of this bore 35 equalizes pressure conditions at both ends of the shaft 25 and avoids subjecting it to unbalanced hydraulic pressure which in a pump such as this may be at a high value.

The opposite gears of each of the sets of gears, such as 4 and 5, are journaled on a fixed stud 36, this stud being fixed against rotary and axial motion and having a central passage 37 therethrough. The inner set of pump gears delivers pressure at its discharge side into a bore 38 formed in the end plate 9, but in order that this pressure may not exert an end thrust on the gears, this end plate 9 is drilled entirely through and this plate 9 and the frame plate 20 together define between them a passage 40 extending inwardly from the passage 38 and opening into a chamber 41 having communication with the bore 37 of the stationary stud. As the pressure in this passage 40 is not exposed to any of the gear faces, it does not produce eccentric axial pressure on the gears, thus eliminating the wear resulting from the eccentric pressures on the" gear in constructions heretofore made and as previously described.

In place of forming the groove 40 in the outer face of the plate 9 which is of hard material, the groove may be formed in the softer casing zplate 20 as shown at 45 in Figure 7. .Whether'the groove leading from the open ing 38 be in the plate 9 or the casing member 20, or if desired partly in both, the plate 9 bridges over-the adjacent face of the gear, thus to avoid a construction producing the axial eccentric thrust thereon hereinbe'fore mentioned. It is, of course, easierzto cut the groove in the relatively soft plate 20 than to cut it in the outer face of the hard plate 9, but in either event the face groove relieves the gear from the heavy facial pressure so that wear on the gear and neighboring parts is much reduced.

The gears 1 and 2 are provided with suitable intake and discharge in a manner ,well. known in the art, and the intake to the gears 3 and 4may be common to that for the gears 1 and 2.

In Figure 6 there is shown a modification in which a single pair of gears considerably ,thicker than shown in Figures 1 to 4 is employed with a correspondingly thicker peripheral casing plate 6a. This construction may have the capacity of the double pump shown' in Figures 1 to 5, but would discharge a. single-:stream. .Here again the bolts 20a which secure the various plates together extend through the end plates 7a and 9 and are threaded into the threaded sockets in the casing member 20. The discharge port may be directly through the end plate 7a corresponding in position tothe discharge from the gears 1 and 2 of the double pump as iswell known in the art.

From the foregoing description ofcertain embodiments of this invention it will be evident to those skilled in the art that various changes and modifications may be made therein without departing from its spirit or scope.

I claim:

1. A dual gear pump comprising a block composed of a series of plates in face to-face contact, two of said plates 4 each having a cut out in which a pair of gears are fitted, said series also including side plates between which said cut out plates are sandwiched to enclose said gears, said block having two separate outlets at the same side face thereof one for each of the respective pairs of gears, a drive shaft extending through said block, one of each pair of said gears being secured on said shaft, a tubular stud within said block, the other gear of each said pair being rotatable thereon, one end of said stud opening out at one of said outlets, the other end of said stud communicating with the discharge ofthe pair of gears adjacent to said other end, the side plate for the last named gears remote from said outlet side of the block having a hole therethrough at the discharge point of said last named gears, said block having a duct therein extending along the face of the last named side plate remote from said gears and connecting said hole with said other end of the tubular stud to provide a discharge passage from said last named pair of gears to one of said outlets.

'2. Apparatus as in claim 1, said block including a cover plate at the side opposite to said outlet side, said duct consisting of a groove in the inner face of said cover plate.

References Cited in the file of this patent UNITED STATES PATENTS 

